[address-policy-wg] 2019-05 New Policy Proposal (Revised IPv4 assignment policy for IXPs)

* Gert Doering

> On Fri, May 31, 2019 at 09:08:30AM +0200, Tore Anderson wrote:
>> Also, I am wondering about the thinking behind giving out /24s
>> by default when the minimum assignment size is reduced /27. Why not
>> right-size the assignment all the way down to the minimum assignment
>> size, thus maximising the amount of future entrants the pool can
>> support? There's nothing special about the /24 boundary for the IXP
>> use case, to the best of my knowledge.
> 
> We briefly touched this in the WG session last Wednesday.  Doing it 
> this way removes the discussion about "larger address block for routing 
> reasons" *if* the IXP in question decides that they do want to announce 
> their prefix.
> 
> So, as written today, "if you don't know", you get a /24 which could
> be routed later.  "If you are sure you're small and do not want this
> announced", you can ask for a /27.../25.
> 
> Not advocating anything, just relaying what was the explanation given.

Right.

Looking at the DFZ, there is only a single advertisement coming out of the current IXP pool¹:

https://stat.ripe.net/widget/routing-status#w.resource=185.1.0.0%2F16

Considering how extremely uncommon this configuration is, I'd prefer it to be the other way around, i.e., that a small IXP with a dozen members would need to explain why they need a /24 in order to get it, otherwise they'd get a /27 by default.

If we give out /27s by default to such small IXPs each /24 in the pool can accommodate 8 IXPs. With the current (and proposed) policy we'd need a /21 to accommodate those same 8 IXPs (as I do not imagine any of them explicitly requesting something smaller than what's on offer by default). This seems wasteful.

[1] I was told on IRC that the reason for the specific advertisement seen is to provide some kind of quasi-OOB Internet transit service to the IXP members. If that is correct it seems to me to possibly run afoul of the first bullet in section 6.1, but whatever.

Tore